server's eye. Reflection at a particular angle from vast sheets of ice, as smooth as glass, might be suggested as the cause of such a display, but how could ice be there without water or atmosphere? The suggestion that has been offered to account for the brightness of Aristarchus and the "ray" systems, namely, that they are composed of metallic dikes and masses which, for various reasons, have escaped oxidation, is recalled by the phenomenon in question. Upon that view we might have to assume that these luminous points indicated the existence of tremendous crystallized masses, with polished surfaces, throwing back the glare of the sunshine like mirrors. But then we should not be far from the view set forth in Richard Adams Locke's celebrated "Moon Hoax," that some of the glittering eminences on the moon are nothing less than enormous quartz-crystals, whose dimensions are measured by miles instead of inches!
The fact that the apparitions of extraordinary luminosity are confined to comparatively very small areas, and are visible only for a short time and at long intervals, must be taken as an indication that the reflecting surfaces to which they are due must be of such a nature, and so disposed, that they can reflect the sun's light to us only when presented at a particular angle to our line of sight; just as a piece of looking-glass, exposed to the sun at a distance, suddenly darts a piercing ray when the eye comes within the plane of reflection. That these surfaces are the flanks of mountains is in the highest degree probable, and this but serves to heighten the impression of their extraordinary nature.
The rapid appearances and disappearances, and the long periods of invisibility, are readily accounted for by the various librations of the moon, whereby it presents its disk to us at a continually varying angle, as it swims along in its "squirming orbit," under the conflicting attractions of the sun and the earth.